512 THE BRAIN OF MAMMALS, BY TH. MEYNERT. 



innermost fasciculi of the roots, pursue a direction opposed to 

 that of the fibrse arcuatse, and run with their convexity 

 directed backwards, through the posterior fasciculi of the 

 anterior column (fig. 258, xn). 



We cannot, however, be certain that these fasciculi are not 

 interrupted by nerve corpuscles, especially in the raphe. Were 

 they uninterrupted, they would certainly accord with the course 

 of the facial nerve. 



A commissure between the two hypoglossal nuclei formed 

 by the decussation of very fine fibres traversing the grey 

 median line behind the anterior column has been described by 

 Gerlach ; and Clarke has shown in longitudinal sections a con- 

 nection between the facialis-abducens nucleus and the hypo- 

 glossal nuclei within the grey matter of the central cavities, 

 in regard to such connections, many difficult peculiarities of 

 course are no doubt open to discovery that may prove of high 

 importance for the physiological comprehension of co-ordinated 

 reflex phenomena. 



The transverse fasciculi in the posterior division of the medulla 

 oblongata form, above the decussation of the pyramids, counting 

 from before backwards, seven orders or arrangements, which are con- 

 tinuous with the following different parts : (1) with the corpora 

 restiformia; (2) with the posterior column (cuneate and slender 

 fasciculi) ; (3) with the internal division of the crus cerebelli ; (4) 

 with the root of the auditory nerve ; (5) with the ascending root of 

 the lateral mixed system ; (6) with the glossopharyngeal and vago- 

 accessorius nuclei ; (7) with the hypoglossal nuclei. 



5, THE CEREBELLUM. 



The centre situated behind the peduncle of the cerebrum 

 the cerebellum the addition of which to the just-described 

 division of the projection system confers upon it its peculiar 

 characteristics, is far more closely proportional in point of 

 Size to the cerebral lobes than is the ganglia of the tegmentum, 

 or the posterior tract of the peduncle. This relative develop- 

 ment affects essentially the lateral portions or hemispheres of 

 the cerebellum, whilst the vermiform process preponderates in 

 the lower forms of brain. Within these hemispheres, however 

 it is the interior region of their upper surface, the alse of the 



